1. Field of the Invention
The invention relates to a composite having two or more layers wherein at least one of the layers is obtained from a polyamide blend.
2. Discussion of the Background
Composites having two or more layers may be used, for example, as a tube for conveying liquids or gases in motor vehicles. The used molding compositions have to have adequate chemical resistance to the fluids conducted, and they have to be stable under all of the mechanical requirements placed upon them, even after long exposure to fuels, oil or heat. Molding compositions based on polyamide have proved successful. However, the composite having two or more layers is subject not only to effects due to the fluid to be conveyed, but also to external effects. Examples of such effects, in the case of tubes laid in the underbody region of motor vehicles, are the action of atmospheric moisture, water spray, road salts, underbody protection, greases and oils. For this reason, the only materials which can be used for tubes of this type are polyamide molding compositions based on PA11, PA12, PA612, PA1012 or PA1212. Although other polyamides, e.g. PA6, PA66 or PA6/66, would cope with exposure to the fluid to be conveyed, and would also have low cost, they have relatively low impact strength and high water absorption, associated with swelling and therefore unacceptable dimensional changes. In addition, PA6 is not sufficiently resistant to zinc chloride. At least the outer layer, therefore, cannot be composed of polyamides of this type.
DE 40 06 870 C1 describes a fuel line intended for motor vehicles which is composed of at least three layers made from at least two different mutually compatible polyamides. This patent discloses that different polyamides have different diffusion profiles for each component of fuel. Therefore, combining different polyamide layers can reduce total fuel permeation.
DE-40 06 870 C1 maintains that PA66 is sufficiently compatible with PA11 or PA12 and that no delamination is observed in piping made from layers of this type. However, this was not confirmed when the work was repeated. Instead, it was found that two coextruded layers one of which is composed of PA11, PA12, PA612, PA1012, or PA1212 and the other is composed of PA6, PA66, or PA6/66, have either no adhesion at all to one another or the adhesion is far from sufficient to give a composite free from delamination over long periods.
EP-A-0 731 308 acknowledges the problem of lack of adhesion between layers made from different polyamides. It discloses a coextruded tube having two or more layers. An outer layer is composed of a PA11 molding composition and an inner layer is mainly composed of PA6. The layers are bonded by a polyolefin-based adhesion promoter.
However, the automotive industry has for some time required increased stability at relatively high temperature. This excludes solutions which include a polyolefin layer, since it has a low heat resistance.
It has also been found that prolonged contact with alcohol-containing fuel, in particular in the presence of heat, rapidly reduces layer adhesion between functionalized polyolefin and polyamide. This adhesion finally falls to values which are unacceptable in industry. The cause of this is thought to be an alcoholysis or hydrolysis reaction.
It is therefore an object of the present invention to provide a composite having two or more layers at least one of which is based on polyamide, wherein all of the layers have an adequate heat resistance.
Another object is to combine two or more layers without the use of a polyolefin layer as adhesion promoter. Combined are a) a layer made from a relatively low-cost polyamide and b) a layer made from a polyamide which has particularly good mechanical properties and low water absorption and is not sensitive to environmental effects.
Yet another object is to combine two polyamide layers in a composite having two or more layers. Each of the polyamide layers have different barrier action for the different constituents of a mixture of solvents or fuels. These polyamide layers should have firm bonding to one another via a suitable adhesion promoter.
A further object is to provide a polyamide-based composite having two or more layers, wherein the adhesion between the layers is very substantially retained even after prolonged contact with alcohol-containing or aqueous media in the presence of heat.
These and other objects have been achieved by the present invention, the first embodiment of which includes a composite having two or more layers and comprising:
a layer I obtained from a molding composition comprising:
a) from 0 to 80 parts by weight of a polyamide selected from the group consisting of PA6, PA66, PA6/66 and a mixture thereof;
b) from 0.05 to 100 parts by weight of a polyamine-polyamide copolymer prepared from the following monomers:
xcex1) from 0.5 to 25% by weight, based on the polyamine-polyamide copolymer, of a polyamine having at least 4 nitrogen atoms and having a number-average molecular weight Mn of at least 146 g/mol, and
xcex2) a polyamide-forming monomer selected from the group consisting of a lactam, a xcfx89-aminocarboxylic acid, an equimolar combination of a diamine and a dicarboxylic acid and a mixture thereof; and
c) from 0 to 80 parts by weight of a polyamide selected from the group consisting of PA11, PA12, PA612, PA1012, PA1212 and a mixture thereof;
wherein a total of the parts by weight of components a), b) and c) is 100;
wherein at least 20 parts by weight of components a) and b) is a monomer unit which is obtained from caprolactam and/or from a combination of hexamethylenediamine/adipic acid; and
wherein at least 20 parts by weight of components b) and c) is a monomer unit which is obtained from xcfx89-aminoundecanoic acid, laurolactam, a mixture of hexamethylenediamine and 1,12-dodecanedioic acid, a mixture of 1,10-decanediamine and 1,12-dodecanedioic acid, and/or a mixture of 1,12-dodecanediamine and 1,12-dodecanedioic acid.
In another embodiment the present invention includes a composite having two or more layers and comprising:
a layer I obtained from a molding composition comprising:
a) from 0 to 80 parts by weight of a polyamide selected from the group consisting of PA6, PA66, PA6/66 and a mixture thereof;
b) from 0 to 100 parts by weight of a polyamine-polyamide copolymer prepared from the following monomers:
xcex1) from 0.5 to 25% by weight, based on the polyamine-polyamide copolymer, of a polyamine having at least 4 nitrogen atoms and having a number-average molecular weight Mn of at least 146 g/mol, and
xcex2) a polyamide-forming monomer selected from the group consisting of a lactam, a xcfx89-aminocarboxylic acid, an equimolar combination of a diamine and a dicarboxylic acid and a mixture thereof; and
c) from 0 to 80 parts by weight of a polyamide selected from the group consisting of PA11, PA12, PA612, PA1012, PA1212 and a mixture thereof;
wherein a total of the parts by weight of components a), b) and c) is 100;
wherein at least 20 parts by weight of components a) and b) is a monomer unit which is obtained from caprolactam and/or from a combination of hexamethylenediamine/adipic acid; and
wherein at least 20 parts by weight of components b) and c) is a monomer unit which is obtained from xcfx89-aminoundecanoic acid, laurolactam, a mixture of hexamethylenediamine and 1,12-dodecanedioic acid, a mixture of 1,10-decanediamine and 1,12-dodecanedioic acid, and/or a mixture of 1,12-dodecanediamine and 1,12-dodecanedioic acid;
wherein the molding composition of layer I is obtained by subjecting a blend comprising polyamide a) and polyamide c) to solid-phase post-condensation.
Yet another embodiment of the present invention includes a composite having two or more layers and comprising:
a layer I obtained from a molding composition comprising:
a) from 0 to 80 parts by weight of a polyamide selected from the group consisting of PA6, PA66, PA6/66 and a mixture thereof;
b) from 0 to 100 parts by weight of a polyamine-polyamide copolymer prepared from the following monomers:
xcex1) from 0.5 to 25% by weight, based on the polyamine-polyamide copolymer, of a polyamine having at least 4 nitrogen atoms and having a number-average molecular weight Mn of at least 146 g/mol, and
xcex2) a polyamide-forming monomer selected from the group consisting of a lactam, a xcfx89-aminocarboxylic acid, an equimolar combination of a diamine and a dicarboxylic acid and a mixture thereof; and
c) from 0 to 80 parts by weight of a polyamide selected from the group consisting of PA11, PA12, PA612, PA1012, PA1212 and a mixture thereof;
wherein a total of the parts by weight of components a), b) and c) is 100;
wherein at least 20 parts by weight of components a) and b) is a monomer unit which is obtained from caprolactam and/or from a combination of hexamethylenediamine/adipic acid; and
wherein at least 20 parts by weight of components b) and c) is a monomer unit which is obtained from xcfx89-aminoundecanoic acid, laurolactam, a mixture of hexamethylenediamine and 1,12-dodecanedioic acid, a mixture of 1,10-decanediamine and 1,12-dodecanedioic acid, and/or a mixture of 1,12-dodecanediamine and 1,12-dodecanedioic acid;
wherein either polyamide a) or c) contains an excess of amino end groups and the other polyamide contains an excess of carboxyl end groups.
The present invention also includes a composite having two or more layers and comprising:
a layer I obtained from a molding composition comprising:
a) from 0 to 80 parts by weight of a polyamide selected from the group consisting of PA6, PA66, PA6/66 and a mixture thereof;
b) from 0 to 100 parts by weight of a polyamine-polyamide copolymer prepared from the following monomers:
xcex1) from 0.5 to 25% by weight, based on the polyamine-polyamide copolymer, of a polyamine having at least 4 nitrogen atoms and having a number-average molecular weight Mn of at least 146 g/mol, and
xcex2) a polyamide-forming monomer selected from the group consisting of a lactam, a xcfx89-aminocarboxylic acid, an equimolar combination of a diamine and a dicarboxylic acid and a mixture thereof; and
c) from 0 to 80 parts by weight of a polyamide selected from the group consisting of PA11, PA12, PA612, PA1012, PA1212 and a mixture thereof;
wherein a total of the parts by weight of components a), b) and c) is 100;
wherein at least 20 parts by weight of components a) and b) is a monomer unit which is obtained from caprolactam and/or from a combination of hexamethylenediamine/adipic acid; and
wherein at least 20 parts by weight of components b) and c) is a monomer unit which is obtained from xcfx89-aminoundecanoic acid, laurolactam, a mixture of hexamethylenediamine and 1,12-dodecanedioic acid, a mixture of 1,10-decanediamine and 1,12-dodecanedioic acid, and/or a mixture of 1,12-dodecanediamine and 1,12-dodecanedioic acid;
wherein components a) and c) are linked by adding a reactive compound which links the polyamide end groups to one another.